Accelerating agent in potash recovery



Patented Apr. 17, 1923.

ours "Fares CORPORATION OF VIRGINIA.

No Drawing.

T 0 aZZ whom it may concern Be it known that we, HARRY WV. CHARLTON andRANDOLPH NORRIS SHREVE, respectively a citizen of Canada and a citizenof the 5 United States, each residing at New York, in the county of NewYork and State of New York, have invented certain new and usefulImprovements Regarding Accelerating Agent in Potash Recovery; and we do10 hereby declare the following to be a full,

clear, and exact description of the invention, in any suitable well knowACCELERATING AGENT IN POTASH RECOVERY.

Application filed March 5. 1921. Serial No. 449,913.

such as will enable others skilled in the art crystallization.

to which it appertains to make and use the same.

This invention relates to a method of accelerating the liberation ofpotassiruusalts during processes of digestion and thereby recovering agreater proportion of'potassiurn raise FWQE.

or New YORK, N. Y., 3? NEW YORK, N. Y., A

parts of water, and digest the mixture at, say, 470? Fahrenheit,corresponding to a pressure of about 500 pounds, for about 40 minutes;when it will be found that about 69% of the total potassium originallypresent in the greensand will appear in the resulting solution in theform of potassium hydroxide. This solution may now be fil tered, thefiltrate evaporated, and the potassiumnitrate, which was added,recovered n manner, as by A surprising accelerating action is found toresult from the addition of the potassium niin a moreexpeditious andless costly manis present.

ner than heretofore proposed.

With these and other objects inview, the invention consists in the novelsteps and combination of steps constituting the process and in the novelcatalytic or accelerating agent employed, all as will be more fullyhereinafter disclosed and particularly pointed out in the claims.

In order that the precise invention may be more clearly understood, itis said:

When a mixture of greensand, lime and water are digested at elevatedtemperatures and under superatmospheric pressures for a suitable period,a very considerable percentage of the potassium is rendered soluble andappears in the digestion liquor as potassium hydrate.

corresponding trate to the digestion mixture, in that with the saidnitrate present a higher yield of potassium from the greensand isobtained, than is the case when no potassium nitrate In a specificinstance, it was found that only 6 {it of potassium present in thegreensand appeared in the soluble form when no potassium nitrate wasused, while more than 68% of said potassium was dissolved, underprecisely the same conditions when potassium nitrate was employed. Inthis case,

the potassium that was dissolved out of the greensand was found to be inthe form of the hydrate, practically all of thepotassium nitrate addedbeing readily recoverable.

In other words, it has been found that the potassium nitrate thusemployed can. after recovery, be used over again and thus made to actsomewhat after the manner of a catalyst to accelerate the dissolving outof the potassium present in the greensand.

In another specific test, 10 parts of cal cium nitrate were added to thedigestion mixture when more than 72% of the potassium present in thegrecnsand was dissolved. But in omitting said calcium nitrate underprecisely the same conditions, less than (32% of potassium the potassiumpresent in the greensand was salt.this action bein accom anied 'ov anfound in the filtrate. In still another test,

using ammonium nitrate, it was found that increase in the yield.

We have discovered that the addition of certain potassium salts speedsup the reaction as well as increases the yield in these cases.

According to this invention, one may take, for example, by weight, say,85 parts of finely divided greensand, add thereto 85 parts of quicklime, or CaO', and 12 parts of potassium nitrate, KNO mixed with 4:25

the potassium yield was increased thereby to 78%, from less than 62%.

Similarly the additions of other salts to the greensand, lime, watermixture before For ex from less than 48% to over 67% (In this case thedigestion period was-only 20 minutes.)

The explanation of the accelerating action of the various salts upon theliberation of the potassium from the greensand is probably due to anincrease in the amount of the calcium hydroxide or of the calcium ion inthe solution, due to the action of the added salt. As evidence of thisprobable explanation I refer to Gmelin-Krauts Handbuch der anorganischenChemie, 7th edition, volume II, part 2, pages 206, 207, 208, in whichmuch data is collected together showing the increase in amount ofcalcium hydroxide or calcium ions in aqueous solution in presence ofvarious dissolved compounds,

in comparison with solubility in water alone. Among such salts whichincrease the solubility of calcium hydroxide, are nitrates of sodium,potassium and calcium sodium sulphate, sodium chloride, ammoniumchloride, etc., etc. same reference showing that while caustic potashand caustic soda solutions dissolve less calcium hydroxide than purewater, yet certain salts, for example calcium nitrate, actuallydissolvein caustic soda and caustic potash solutions to such an extentas to increase the amount of calcium ions present,

over what would be present'under the same conditions without the calciumnitrate.

Although this process has been exemplified largely by its applicationtogreensand, yet it is found that it will ope ate on the distantlyrelated leucite, phonolite, etc., and other potassium silicate bearingrocks, in a manner similar to that disclosed in connection withgreensand.

In carrying out the digestion with greensand, etc., it is preferred togrind it, preferably to pass a screen of 200 mesh, as the Data is alsogiven in this reaction is hastened and the yield accordingly increased.

Although the above examples have employed pressures of about 500 pounds,such pressures are not at all necessary, because pressures all the wayfrom,'say 100 pounds up to over 500 pounds may be employed, providedthat the time of digestion is varied accordingly. It is found, ofcourse, that the higher the pressure the less will be the time ofdigestion.

It is obvious thatthose skilled in the art may vary the details of theprocess without departing from the spirit of the invention, andtherefore we do not wish to be limited to the above disclosures exceptas may be required by the claims.

We claim:

1. The process of acceleratingthe recovery of the potassium contained ingreensand, which consists in digesting said greensand with potassiumnitrate, and milk of lime under a super-atmospheric pressure and at acorresponding temperature, substantially as described.

2. The process of recovering combined potassium from greensand whichconsists in heating under superatmosphericpressure said material admixedwith lime, water and an accelerating agent containing potassium nitrate,substantially as described.

3. The process of accelerating the action of lime and water indissolving potassium from greensand when heated under superatmosphericconditions, which consists in adding potassium nitrate to armixture ofsaid lime, water andsand, substantially as described.

In testimony whereof we tures.

HARRY V. CHARLTON. RANDOLPH NORRIS SHREVE.

